1. Technical Field
The techniques described herein relate generally to comparators and in particular to a comparator with offset compensation and improved dynamic range.
2. Discussion of the Related Art
Comparators are used in many applications for comparing two input signals. For example, comparators are important building blocks of analog-to-digital converters (ADCs). An important parameter of a comparator is its resolution, which is the minimum voltage difference that can be detected. The resolution of a comparator can directly limit the accuracy of an ADC.
The mismatch of transistors within a comparator can create an offset voltage that limits the resolution of the comparator. To address this problem, comparators have been designed that compensate for the offset voltage. For example, FIG. 1 shows a comparator 100, as described in U.S. Published Patent Application 2010/0237907, that compensates for the offset voltage of its components, among other functions.
Comparator 100 is formed of a first stage 10 and a second stage 20. The first stage 10 is a pre-amplifier stage that can reduce the output switching noise and amplify the input signal to increase the resolution of the comparator. The first stage 10 substantially forms a voltage/current converter which, during an autozeroing step, stores an offset-compensated bias condition so that the offset voltage can be compensated.